Intramedullary nail

Abstract

Tibial intramedullary nail for insertion into the medullary canal of the tibia, comprising a first anchor portion (2) at its own proximal end zone, having at least one transverse through hole (21) suitable for allowing the passage of a first locking screw (3), a stem (4) extending longitudinally from said first anchor portion (2), a second anchor portion (5) at its own distal end zone longitudinally opposite to the first anchor portion (2), which second anchor portion (5) has at least one first transverse through-slot (51) suitable for allowing the passage of a second locking screw (6).

Description

[0001] DESCRIPTION

[0002] "INTRAMEDULLARY NAIL"

[0003] Technical Field

[0004] This invention relates to an intramedullary nail. Specifically, this invention concerns an intramedullary nail for the tibia, designed to immobilize the ankle joint.

[0005] Ankle immobilization, or more precisely, coarctation of the tibiotalar joint and talocalcaneal joint (TTC), may be required in the presence of pathologies that cause instability, chronic pain, or deformity, or even in the case of complex or multiple fractures involving the talus and calcaneus.

[0006] This coarctation is often performed in cases of chronic joint instability due to pathologies such as rheumatoid arthritis or other degenerative conditions.

[0007] State of the Art

[0008] The use of a tibial nail in this context is intended to stabilize the affected area, promote joint fusion, and thus improve limb function.

[0009] During surgery, the surgeon typically uses a drill to create a canal in the calcaneus, talus, and tibia, which will serve as a guide for the nail.

[0010] The tibial nail, which is a long metal rod of high mechanical strength, is inserted into the calcaneus through the aforementioned canal until it reaches, after also passing through the talus, the proximal end of the hole made in the tibia.

[0011] Using well-known imaging techniques, the surgeon ensures that the nail is correctly positioned through the tibiotalar joint and talocalcaneal joint. Once positioned, the nail is secured in place using locking screws that pass transversally through the tibia and the nail itself.

[0012] These screws ensure the nail remains stable and prevent any unwanted movement.

[0013] More laborious is the attachment of the distal portion of the nail to the talus and calcaneus, respectively.

[0014] In fact, attaching these bones to the nail must ensure optimal compression of the tibia to achieve the desired coarctation.

[0015] Achieving the appropriate compression between the calcaneus, talus, and tibia is not easy, as the surgeon essentially requires compressing these bones and simultaneously applying the necessary locking screws to the tibial nail.

[0016] This not-easy operation is made even more complicated by the bony structure of the calcaneus, the inner part of which, due to its mechanical characteristics even in the absence of specific pathology, does not offer a stable anchorage to the relative locking screw to the tibial nail.

[0017] Object of the Invention

[0018] The object of the present invention is to provide an intramedullary tibial nail that overcomes the drawbacks of the prior art while being simple, cost-effective, and practical to use.

[0019] A further object of the present invention is to provide an intramedullary tibial nail that achieves effective reciprocal compression of the bones involved in coarctation of the tibiotalar and talocalcaneal joints. Brief ion of the

[0020] The technical characteristics of the invention, in accordance with the aforementioned objects, are clearly described in the appended claims, and its advantages are evident from the detailed description that follows, with reference to the appended drawings, which illustrate an exemplary and non-limiting embodiment thereof wherein:

[0021] - Figure 1 illustrates, in a schematic perspective view, with parts in transparency as an X-ray, a tibial nail according to the present invention applied to a patient;

[0022] - Figure 2 shows, in an exploded perspective view, the tibial nail according to the present invention with some screws suitable for its implantation;

[0023] - Figure 3 shows, in a schematic perspective view, the tibial nail shown in the previous figures with some screws in its first configuration of use;

[0024] - Figure 4 shows a schematic perspective view of the tibial nail of Figure 3 in a second configuration of use;

[0025] - Figure 5 shows a schematic perspective view from a different angle of the tibial nail of Figure 4;

[0026] - Figure 6 shows a schematic side elevation view of the tibial nail of the previous figures;

[0027] - Figure 7 shows a schematic bottom plan view of the tibial nail according to the present invention;

[0028] - Figure 8 shows a sectional view along the line VIII-

[0029] VIII of Figure 7; - Figures 9 and 10 show, in respective perspective views from different angles, a detail of the tibial nail according to the present invention;

[0030] - Figure 11 shows a schematic elevation view of the detail of Figures 9 and 10;

[0031] - Figure 12 illustrates, with also an enlarged scale detail, the tibial nail illustrated in Figure 3 with dissected parts to better highlight others.

[0032] Detailed Description

[0033] As illustrated in figure 1, the reference number 1 illustrates a tibial nail made in accordance with the present invention, implanted in a patient's tibia and engaged with the underlying talus and calcaneus.

[0034] As illustrated in figure 1, the intramedullary tibial nail 1 according to the invention is designed to be inserted into the medullary canal of the tibia T and comprises a first anchor portion 2 located at its proximal end.

[0035] In the following discussion, for brevity, it will also be referred to simply as nail 1 or tibial nail 1.

[0036] In the aforementioned first anchor portion 2, nail 1 has a transverse through-hole 21 designed to allow the passage of a first locking screw 3, visible in figure 1.

[0037] The first locking screw 3 is designed to engage the patient's tibia T.

[0038] In use, an additional locking screw 3a, also visible only in figure 1, is advantageously applied below the first screw 3, designed to make the fixation of nail 1 to the tibia more stable and effective. The locking screw 3a is inserted inside a through-hole 22, visible in figure 2, made at the first anchor portion 2.

[0039] The tibial nail 1 includes a stem 4 extending longitudinally from the aforementioned first anchor portion 2 and developing distally therefrom.

[0040] As illustrated in figures 1 and 2, the tibial nail 1 comprises a second anchor portion 5 at its distal end zone longitudinally opposite the aforementioned first anchor portion 2.

[0041] As is accepted practice in the medical field, the distal and proximal indications referring to parts of femoral nail 1 are to be understood with respect to the center of the body of a patient in which nail 1 itself is implanted.

[0042] According to what is shown in figure 2, the second anchor portion 5 has a first transverse through-slot 51 suitable for the passage of a second locking screw 6. The second anchor portion 5 has a second transverse through-slot 52 designed to allow the passage of a third locking screw 7.

[0043] Advantageously, as illustrated by way of example in figure 1, the second locking screw 6 passing through the first slot 51 is designed, in use, to screwingly engage with the patient's calcaneus C.

[0044] The third locking screw 7 passing through the second slot 52 is designed, in use, to screwingly engage with the patient's talus A.

[0045] Advantageously, as illustrated in figure 2, the nail 1 has an additional through-hole 53 suitable for engagement with a calcaneus locking screw 8 C, to be used in addition to the second screw 6 described above. The locking screw 8 is not illustrated in the use configuration of tibial nail 1 shown in figure 1. According to what is illustrated in the cross-sectional view in figure 8, the nail 1 has a central longitudinal cavity 9 that runs continuously along its stem 4 and along the second anchor portion 5, until it flows outward at an opening 10 located at the distal end of the nail 1 itself.

[0046] The nail 1 advantageously includes a threaded 11 grub. The threaded grub screw 11 screwingly engages within the central cavity 9, in an internally threaded section thereof, located at least partially at the aforementioned second slot 52.

[0047] In particular, the aforementioned threaded section also extends distally beyond the aforementioned second slot 52, towards the first slot 51, so as to allow the threaded grub screw 11 to be securely screwed in without it axially occupying the internal space of the second slot 52, as shown in the configuration illustrated in figure 8.

[0048] With reference to what is illustrated in figures 8 to 11, the tibial nail 1 comprises, located internally within the aforementioned central cavity 9 at the first slot 51, a wire-shaped elastic member 12.

[0049] The wire-shaped elastic member 12 is configured to screwingly engage with the aforementioned second locking screw 6 when the latter is, in use, inserted into the first slot 51. As clearly visible in figures 9 to 10, and in particular in figure 11, the wire-shaped elastic member 12 is U-shaped and has two longitudinal arms 121 and a transverse connecting section 122 between these two longitudinal arms 121.

[0050] Advantageously, as illustrated in figures 9 to 11, the two longitudinal arms 121 have a straight extension, are parallel to each other, and identify a respective lying plane which in figure 11 is parallel to the plane shown in the figure.

[0051] Again with reference to figure 11, the aforementioned transverse connecting section 122 having a curved profile lies on a plane perpendicular to the above- mentioned plane on which the longitudinal arms 121 lie. According to embodiments not illustrated, the plane on which the curved transverse connecting section 122 lies is incident on the plane of the longitudinal arms 121 at an angle other than 90°.

[0052] As shown in figures 8 to 11, for each of its longitudinal arms 121, the elastic member 12 has, at its free ends opposite the connecting section 122, respective pins 123 designed to rotatably engage in special holes 13 made in the nail 1 itself.

[0053] The holes 13 are through-holes and open into the central cavity 9 of the nail near the proximal end of the first slot 51.

[0054] Advantageously, each aforementioned pin 123 is defined by the metal wire with which the entire elastic member 12 is made, bent at 90° with respect to the adjacent longitudinal arm 121. Advantageously, the elastic member 12 is made of titanium alloy wire.

[0055] Preferably, the elastic member 12 is made of biocompatible ELI grade 5 titanium alloy wire.

[0056] Advantageously, the entire tibial nail 1 is also made of the same material.

[0057] It is, in fact, good practice to use the same material for all components in implanted medical devices to limit the risk of electron migration.

[0058] The diameter of the titanium alloy wire used to make elastic member 12, must be large enough to allow the second screw 6 to screwingly engage with the wire.

[0059] In other words, the wire must be large enough to at least partially penetrate the thread; that is, its diameter must be equal to or smaller than the pitch of the second screw 6.

[0060] Advantageously, according to one embodiment that has provided completely satisfactory experimental results, the diameter of the titanium alloy wire used to make elastic member 12 is 0.9 mm.

[0061] The elastic deformability of the elastic member 12, due to both its shape and the material used to manufacture it, is advantageously exploited both for the insertion of the elastic member 12 itself into its housing within the central longitudinal cavity 9 and for its engagement with the second screw 6.

[0062] With regard to the insertion of the elastic member 12 into its operating position, in fact, thanks to its elastic deformability, the two pins 123 are brought together and subsequently released to insert themselves into the respective through-holes 13. With regard to engagement with the second locking screw 6, when the latter is screwed onto the longitudinal arms 121, these are also capable of elastically deforming to follow the effective diameter of the screw 6.

[0063] In other words, the initial taper of the second screw 6 allows it to fit between the two longitudinal arms 121 of the elastic member 12 even if the distance between these arms 121 is less than the external diameter of the second screw 6 itself.

[0064] In addition, the elastic deformability allows the elastic member 12 to adapt in engagement with the screws that also have core diameters greater than the distance, in undeformed configuration, between its longitudinal 121 arms.

[0065] In use, starting from an implant configuration such as that illustrated in figure 1, once the nail 1 has been inserted through special holes drilled in the calcaneus C and the talus A, the surgeon inserts it from bottom to top into the medullary cavity of the tibia T, stopping its penetration at a specific point, advantageously identified with radiographic instruments.

[0066] After applying the first screw 3 and screw 3a to the first anchor portion of nail 1, the nail 1 is therefore stably fixed to the tibia T.

[0067] Once this is done, the surgeon proceeds with the insertion of the third screw (7), which engages in the talus (A) and in the nail (1), crossing the latter's second slot (52). The threaded grub screw 11, as mentioned, screwingly engages in a section, that is internally threaded, of the central cavity 9, partly interposed between the two slots 51, 52 first and second, and partly obtained along the second slot 52 itself.

[0068] The threaded grub screw 11 is screwed in to adjust the position of the third screw 7 along the second slot 52. In other words, using the grub screw 11, it is possible to reciprocally move the third locking screw 7 in an axial direction relative to the tibial nail 1. This movement, provided that the tibial nail 1 is integrally fixed to the tibia T at the first anchor portion 2, advantageously allows the surgeon to adjust the compression of the talus A, in which the third locking screw 7 is fixed, relative to the tibia T itself.

[0069] In other words, by screwing the fixing grub screw 11 into its seat, moving from the configuration shown in figure 3 to that shown in figure 4, a relative movement in the longitudinal direction of the nail 1 is obtained between the tibia T to which the nail 1 is fixed, and the talus A to which the third locking screw 7 is fixed.

[0070] Thanks also to the threaded grub screw 11, the surgeon is able to stably position the talus A on the tibia T. Once this is done, for effective coarctation of the foot joint, the calcaneus C must be fixed to the tibia T-talus A complex.

[0071] To do this, the surgeon, holding the calcaneus C in the desired position, inserts the second screw 6 into the calcaneus itself through the first slot 51. As it passes through the first slot 51, the second screw 6 screwingly engages, as described above, with the longitudinal arms 121 of the elastic member 12.

[0072] The engagement of the second locking screw 6 with the longitudinal arms 121 ensures that a longitudinal translation (in the direction of extension of nail 1) between the nail 1 and the second screw 6 does not compromise the connection between them.

[0073] In other words, the engagement of the second screw 6 with the elastic member 12, and with the nail 1 to which the elastic member is fixed, is also ensured as a result of relative sliding between the screw 6 and the elastic member 12, due to the slot 51 and the longitudinal development of the arms 121 on which therefore the thread of the screw 6 itself engages slidingly.

[0074] The curvature of the connecting section 122 is apt to allow a wrench to pass through the threaded grub screw 11.

[0075] Advantageously, the grub screw 11 features a hexagonal recess, and the driving tool, not shown, is a standard hex key shaped to match said recess.

[0076] As illustrated in figure 12, the transverse connecting section 122 of the elastic member 12 is designed to screwingly engage with its end portions close to the longitudinal arms 121, the locking screw 8 transversally with respect to the aforementioned second locking screw 7.

[0077] The ability of the elastic member 12 to screwingly engage with both the second locking screw 6 (with the longitudinal arms 121) and the screw 8 (with the transverse section 122) advantageously allows the screws 6 and 8 to be kept stably anchored to the tibial nail 1 even in the presence of a bone such as the calcaneus C, which, due to its specific morphological characteristics, does not offer particular grip to the screws themselves.

[0078] In other words, the anchoring between the tibial screw 1 and the locking screws 6 and 8 of the calcaneus C allows for a certain stability of the implant as a whole, even in the absence of adequate mechanical characteristics of the calcaneus C.

[0079] Referring again to figure 12, it should be noted that at the bend in the titanium alloy wire, between the pins 123 engaged in the holes 13 and the respective adjacent longitudinal arms 121, the elastic member 12 defines an abutment for the threaded grub screw 11.

[0080] In other words, once the threaded grub screw 11 has been inserted into the appropriate threaded section of the central cavity 9 and the elastic member 12 has also been placed in its seat (with the pins 123 inserted in the respective holes 13), the threaded grub screw 11 is prevented from separating and coming out of the tibial nail 1 thanks to the shape-related impediment of the elastic member 12.

[0081] This circumstance is particularly advantageous, as it allows the various aforementioned components of the tibial nail 1 to be pre-assembled during the packaging of the surgical kit in a clean room, thus relieving the surgeon from having to carry out this operation immediately prior to surgery.

[0082] Preferably, therefore, after inserting the elastic member 12 during assembly, the threaded grub screw 11 is unscrewed until it abuts against the elastic member 12. This configuration ensures that the transverse through-slot 52 is completely clear for insertion of the third screw 7 for locking the talus.

[0083] In fact, the length of the threaded grub screw 11 and the extension of the threaded portion of the cavity 9 are such that, when abutting against the elastic member 12, the threaded grub screw 11 does not obstruct the through-slot 52.

[0084] ~k~k~k

Claims

CLAIMS1. Tibial intramedullary nail for insertion into the medullary canal of the tibia, comprising:- a first anchor portion (2) at its proximal end zone, featuring at least one transverse through- hole (21) designed to allow the passage of a first locking screw (3),- a stem (4) extending longitudinally from said first anchor portion (2),- a second anchor portion (5) at its distal end zone longitudinally opposite said first anchor portion (2), which second anchor portion (5) features at least one transverse through-slot (51) designed to allow the passage of a second locking screw (6), characterized in that it comprises an elastic wire member (12) arranged internally of said nail at said first hole (51) and configured to engage at least one thread of said second screw (6).

2. Tibial intramedullary nail according to claim1, characterized in that said elastic wire member (12) is U-shaped and has two longitudinal arms (121) and a transverse connecting section (122) between said two longitudinal arms (121).

3. Tibial intramedullary nail according to claim2, characterized in that said transverse connecting section (122) has a curved development.

4. Tibial intramedullary nail according to claim3, wherein said two longitudinal arms (121) have a rectilinear development, are parallel to each other and identify a respective lying plane, characterized in that said transverse connecting section (122) having a curved development lies on a plane incident to said lying plane of said longitudinal arms (121).

5. Tibial intramedullary nail according to claim4, characterized in that said plane on which said curved transverse connecting section (122) lies is substantially perpendicular to said plane in which said longitudinal arms lie (121).

6. Tibial intramedullary nail according to any of the preceding claims 2 to 5, characterized in that said transverse connecting section (122) is configured to screwingly engage with at least one thread of a further locking screw (8) transverse to said second (6) screw.

7. Tibial intramedullary nail according to any of the preceding claims 2 to 6, characterized in that for each of its longitudinal arms (121), the elastic member (12) has, at its free ends opposite said connecting section (122), respective pins (123) capable of rotatably engaging in special holes (13) made in the nail itself.

8. Tibial intramedullary nail according to claim7, characterized in that each said pin (132) is defined by the wire that forms said elastic member (12), bent at 90° with respect to said longitudinal arm (121).

9. Tibial intramedullary nail according to any of the preceding claims, wherein at said second anchor portion (5) there is a second transverse through-slot (52) suitable for allowing the passage of a third locking screw (7), characterized in that it comprises a threaded grub screw (11) which screwingly engages within said second slot (52) to adjust the position of said third screw (7) along said second slot (52).

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